Serum Bicarbonate

Function

Serum Bicarbonate (HCO3-) is a vital electrolyte and a critical component of the body's buffering system. It plays a central role in maintaining the pH of the blood within a very narrow, slightly alkaline range (7.35 to 7.45). Bicarbonate is primarily regulated by the kidneys, which excrete or reabsorb it to compensate for acid-base imbalances, and the lungs, which manage carbon dioxide (CO2) levels.

Why it is Ordered

This test is typically included in a Basic Metabolic Panel (BMP) or Comprehensive Metabolic Panel (CMP). It is used to evaluate the patient's electrolyte balance and respiratory or metabolic health. It is particularly important for patients with kidney disease, respiratory distress, or severe vomiting and diarrhea, as these conditions rapidly shift the body's acid-base status.

Associated Conditions

• Metabolic Acidosis: Characterized by low bicarbonate levels; causes include diabetic ketoacidosis (DKA), kidney failure, and severe diarrhea.
• Metabolic Alkalosis: Characterized by high bicarbonate levels; causes include prolonged vomiting (loss of stomach acid) and excessive use of diuretics.
• Respiratory Compensation: In chronic lung diseases like COPD, the kidneys may retain bicarbonate to compensate for high CO2 levels (respiratory acidosis).
• Renal Tubular Acidosis (RTA): A condition where the kidneys fail to properly acidify the urine, leading to low serum bicarbonate.